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What are the risk factors or causes of uterine fibroid tumors?

November 4, 2006 — EclecticGeek

Several months ago, I discovered a review article that looked at the current literature and analyzed the risk factors involved with uterine fibroid tumors. I often leave a link to this paper in my responses around this site and finally decided to do a little write-up of my own. Don’t be put off by the name. It’s just a fancy way to say “Uterine Fibroid Risk Factors”. For the truly geeky, there are a BUNCH of reference papers at the end of the review article. I’ll include a link to the web site and also the PDF file.

[Edited to add: One of my visitors was having problems accessing information from the original article so I uploaded the PDF file to my domain. If the PDF file listed above does not work for you, try here: Etiology and Pathogenesis of Uterine Leiomyomas: A Review (.pdf). Also, here’s a link to download the free Adobe Reader software to view PDF files.]

Uterine leiomyomas, or fibroids, are the most common tumors of women in the United States. The clinical effects of these tumors are related to their local mass effect, resulting in pressure upon adjacent organs, excessive uterine bleeding, or problems related to pregnancy, including infertility and repetitive pregnancy loss.

So, what are the causes or risk factors of uterine fibroid tumors?

The article discusses the risk factors of uterine fibroids in isolation but, keep in mind, there is often overlap or interaction. The size, number, and location will depend on a combination of a number of them. This table summarizes the results. (Click the thumbnail to view a larger image.)

Menarche

There is a suggestion of slightly increased risk of fibroids associated with early menarche.

Starting menstruation at a young age increases your risk.

Age

An increase with age in the prevalence of fibroids during the reproductive years especially a rapid increase in fibroid diagnoses among women in their forties.

Increased age (late reproductive years) increases your risk but…
this could be the result of increased growth of already existing fibroids.

Obesity

Several studies have found an association between obesity and an increased incidence of uterine leiomyomas.

A higher weight or Body Mass Index increases your risk.

Racial Differences

Uterine fibroids are more prevalent in black women than white women. In one study, 73% of black women and 48% of white women had uterine fibroids by ultrasound examination. In a study of premenopausal nurses in the United States, the incidence rates among these two groups [Asians and Hispanics], determined by ultrasound or hysterectomy, were similar to those of the white women.

African-American women are at increased risk.

Tamoxifen

Several clinical studies have now reported the growth or enlargement of uterine fibroids in breast cancer patients undergoing tamoxifen therapy.

Tamoxifen use increases your risk.

Parity

Several studies have shown an inverse relationship between parity and the risk of fibroids. A relative risk of fibroids among parous women of 0.5, compared with nulliparae, and a progressive decline in risk relative to the number of births have been reported.

Having no children (nullparity) increases your risk. Having more children decreases your risk.

Menopause

A reduced risk of fibroids requiring surgery in postmenopausal patients…
…postmenopausal leiomyomas were smaller and fewer.

Menopause decreases your risk.

Smoking

Several studies have revealed a reduced risk of fibroids associated with current smoking, but not past smoking. In one study, current smokers had a 50% reduced risk of uterine myomas requiring surgery.

Smoking decreases your risk.

Exercise

Former nonathletes were found to be 1.4 times more likely than former athletes to develop benign uterine tumors.

Exercise decreases your risk.

Diet

…modulation of the diet can influence estrogen metabolism in premenopausal women, which may in turn influence the risk for fibroids.

The studies looked at low-fat/high-fiber diets and vegetarian vs. nonvegetarian diets. Results were not conclusive.

Consuming a low-fat/high-fiber diet may decrease your risk.

Geographic Differences

Reports suggest that uterine fibroids occur commonly in women in many parts of the world.

This inquisitive geek with fibroid tumors ™ blog has received hits from over 60 countries so I’m inclined to believe that.

Oral Contraceptives

Reports in the literature present inconsistencies with regard to the effect of oral contraceptive (OC) use upon the growth of myomas. These conflicting findings with regard to the effect of OCs upon the growth of myomas may relate to the differing content of estrogen and the type of progestogen in each specific OC preparation.

Use of oral contraceptives may increase your risk.

Hormone Replacement Therapy

Fibroids are expected to shrink after menopause, but hormone replacement therapy (HRT) may prevent this shrinkage and may even stimulate growth.

More studies with mixed results.

Use of HRT may increase your risk.

Xenoestrogens

A diverse group of exogenous compounds, xenoestrogens, possesses the potential to disrupt normal estrogenic function as a result of either estrogenic agonist or antagonistic effects. No common chemical structure is predictive of estrogenic activity, and such substances may originate from dietary, industrial, or pharmaceutical sources.

I’m interested in statistics regarding fibroid rates in women around the world. I’m from the United States but living now in Central America. Are there any countries that have significantly lower rates? Where should I look for these numbers?

I am 54 and have known for a while I have 2 large fibroids..I just had a vaginal ultrasound for abnormal bleeding…results were the tumors are still there but have shrunk only a bit..had thought they would go away with menopause..I am having bladder pressure and off and on cramping and discomfort..scared I have cancer….its hard to find anyone or any information on fibroids after menopause…please help..

Becky, you’ll notice not very many women post here… the person who posted before you posted over a year ago! So, you may want to look at other sections on this board and ask there…

Also, I’m 53 and I’ve been having sporadic periods… are you sure it isn’t a period? I sometimes have two periods then skip one or two… some are lighter some a little heavier — and I’ve had doctors say it is perfectly normal, and others who have worried a bit. But I’m fine, so first of all, don’t assume it is abnormal – your body may just be squeezing out a few more eggs once in a while.

That said, I and am considering all of the procedures mentioned on this blog even though I’m not having major bleeding problems any more (I had an endometrial ablation), but I am on hormone replacement therapy, so I don’t expect mine to shrink anytime soon. Even when I was off the hormones for about a year, they didn’t shrink… so I’d say, look into all of the procedures and don’t let doctors bully you into a hysterectomy if they aren’t certain you have cancer and you don’t want a hysterectomy – there are other options. Good luck!

I have fibroids but know little about them. During my exam, the nurse told me that they were large. She was “certain” I would have to have a hysterectomy. My sono is in a couple of weeks. Still awaiting results of my pap. During my pap and the compression against my uterus and her pushing down, she hit something that raised me off of the table in pain. Since my exam last week, I have been in pain. Not just “normal” post exam pain but don’t want to stand straight up and feels almost like my insides are about to fall out???? TMI
The more I read the more confused I am. I have called the Dr. regarding the pain but haven’t gotten a return call.

My symptoms were HEAVY bleeding, constant pressure, fatigue and looking like I am a few months pregnant.
I just turned 43, I am not obese and pretty healthy so the mention of fibroids and hysterectomy has me very scared.

Can anyone suggest questions that I should ask my doctor?
If the fibroids are very large and numerous, is there any other option besides hysterectomy?

Hi Valerie,
I am 46 athletic, white, slim, have 2 children all of the things that you would think would put me at lower risk for fibroid development, but I learned that I had an 18 cm fibroid in my pelvis in February. It was a pedunculating fibroid, which means it grew on a stem outside of my uterus and therefore my periods were fairly normal. The first MD recommended a vaginal hysterectomy. I got a second opinion and went with that. I just had an abdomenal myomectomy via laparotomy on Monday. I had very little discomfort until the internal exams started. Although I did not have pain during the exam like you did, afterward I had a lot of pressure and discomfort for several days. I felt like my fibroid found a nice comfortable place to hide and the exam moved things around. All of my biopsies have been negative. I would always get a second opinion. If you haven’t discovered it yet there is a great site called http://www.hystersisters.com.